Ondina is tasked with teaching young mermaids. Rita introduces Weilan, a Chinese mermaid, who will be staying with them. On the way to the Full Moon Ceremony, the girls encounter a water dragon. Weilan warns that there is no way to stop it. Written by grrlpunk

Rita asks Ondina to keep Weilan, who is staying in the grotto, out of trouble. Joe tells David that he has called the Marine Police about the sea monster (but they didn't believe him) and that he will be calling the Marine Park, as well. Mimmi is reunited with Chris, who is now a dolphin trainer at the Marine Park. Weilan runs into Zac at the café where David warns them about his brother's actions. Weilan tries some clothes inside and overhears Ondina talk about her to Evie. Weilan confronts Ondina and learns that she thinks that Weilan has brought the water dragon and is endangering her Pod. Dr. Ross asks Joe to take Karl and dive around Mako Island to investigate Joe's sea monster. Ondina brings her class to the Moon Pool, the magical heart of Mako Island, to teach them. Weilan visits Mimmi at work and they discuss her confrontation with Ondina, the water dragon, and the loss of her Pod. Joe informs David that two of the Marine Park's best men are investigating the sea monster.... Written by grrlpunk

Mimmi discovers Arctic Sea lavender growing. While Rita, Weilan, and Evie are at school, Mimmi cooks Arctic marshmallow and follows her recipe closely. It turns out wonderfully and Ondina says she could do it too, even though she normally just makes up recipes as she goes. At land school, Zac is doing poorly in Mrs. Trumble's class and Weilan, who is a straight A student, is seated next to him from now on. She agrees to help him study but, even with her help, he just can't seem to remember the information. At Zac's behest, Weilan does a knowledge transference spell on him. The 10th level Eastern mermaid spell doesn't appear to work. The next morning, Zac and Weilan's hair has swapped! They take the test, and Zac gets a 98, which makes their teacher suspicious that he has cheated. She brings him into Rita's office and has called his father, the head of the school board. Meanwhile, Cam and Evie try to help Weilan remember what she did so the spell can be reversed. Unfortunately, she... Written by grrlpunk

Evie wants someone to teach her how to use her Moon Ring safely. Mimmi elects Ondina and her first lesson is moving a mortar and pestle in the grotto. Weilan heckles that Ondina's lesson is ordinary and tells Evie about tricks her Pod did for fun. Mimmi then tells of when she and Ondina first got theirs and would freezy scare local fishermen. At the Ocean Café, Zac and Cam hear David arguing with his brother Joe because he has made the decision to close the café. Evie's father Doug reminds her that she's been slacking on her chores and tasks her with cleaning the kitchen and doing all the piled up dishes. She uses the power of her Moon Ring to mop but it soon seems to have a mind of its own. Zac and Cam brainstorm ways Carly and Evie won't lose their jobs. Zac, Ondina, Mimmi, and Weilan arrive to help Evie but the mop gets loose. Cam approaches Joe with a business proposition. Ondina, Mimmi, and Weilan use freezy scare to destroy the mop. Cam debuts Carly and the house band's ... Written by grrlpunk

Veridia and the Mermaid Council summon Rita for her advice on how to take on the dragon.Ondina, Mimmi, and Weilan brainstorm their own ideas and come up with crossing a Northern shrinking spell with a containment spell and trapping it in a Chinese puzzle box.Carly asks Cam to take dance lessons with her. He voices his concerns to Evie who reminds him that they have to do things that Carly likes and he needs to put in some effort. Ondina and Weilan search the local market for a puzzle box. After no luck, they try one last shop and get one for a bargain price. Zac and Evie show Cam their dance moves before trying to teach him. The mermaids work on the puzzle box and spell to contain the dragon without a break. Cam becomes frustrated with learning to dance and voices his feelings without realizing that Carly is behind him. He tries to make amends with her and she lets him off the hook, for good. That night, while Weilan is sleeping in the grotto, Poseidon gets sucked inside the puzzle ... Written by grrlpunk

Evie's moon ring lesson with Ondina takes an unexpected turn. At the Marine Park, Mimmi discovers the real reason for a rescued dolphin's distress.

Zac begs Weilan to teach him an Eastern spell that he plans to use against the dragon. Mimmi and Ondina cover for David at the Ocean Cafe, but they encounter problems with Joe and a water ball.

On the eve of the full moon, Mimmi and Ondina defy Veridia's order of watching the hatchlings. Evie becomes suspicious when she spots Zac and Weilan meeting in secret again.

Feeling guilty for Evie's loss, Weilan runs away. Mimmi and Ondina try to restore Evie's tail.

Zac finds a shell in Mako. Without realizing it's magical, he makes a wish, sending the mermaids five years back in time.

While teaching the younger mermaids how to walk on land, Ondina and Weilan lose a mermaid in Mako that soon, runs into Chris and Karl on the beach.

Mimmi and Chris go on their first date and Ondina does everything to protect her. Cam makes changes to the Café.

A priceless artifact recovered by a deep-sea treasure hunter provides a clue as to how the mermaids can defeat the water dragon.

The vision reappears to Mimmi and Zac, this time speaking to them. Weilan learns a new detail about the dragon legend that suggests Nerissa is alive.